Control circuit for signal transmitting and receiving apparatus



March 14,1939. AJA: COLLINS 2,150,362.

CONTROL CIRCUIT FOR SIGNAL TRANSMITTING AND RECE'IVINQ APPARATUSOriginal Filed Feb. 1, 1937 4 Sheets-$heet l Ma Z0 ,9. gilllill 25 I FIN ENTORf 1 mam ATTORNEY March 14, 1939.

A. A. COLLINS CONTROL CIRCUITFOR SIGNAL TRANSMITTING AND RECEIVINGAPPARATUS 4 Sheets-Sheet 2 Original Filed Feb. 1, 1937 ICE 5 a A rTbRNEYMarch 14, 1939.

CONTROL CIRCUIT FOR SIGNAL TRANSMITTING AND RECEIVING APPARATUS OriginalFiled Feb. 1, 1937 4 sheets-sheet :5

INVENTOR.

d lrfomvm .March 14, 1939. A. A. COLLINS "CONTROL CIRCUIT FOR SIGNALTRANSMITTING AND RECEIVING 'APPARATUS Original Filed Feb. 1, 1937 4Sheets-Sheet 4 67 Fir-l U Z INVENTOR.

. A. 7 5 BY Fir 5 re: 6 a 28 ATTORNEY Patented Mar. 14, 1939 CONTROLCIRCUIT FOR SIGNAL TRANS- MITTING AND RECEIVING APPARATUS Arthur A.Collins,- Cedar Rapids, Iowa Original application February 1, 1931,Serial No.

Divided and this application Novemher 4, 1937, Serial No. 172,837

4 Claims;

My invention relates broadly to signal transmitting and receivingapparatus and more particularly to a circuit arrangement for theautomatic control of high frequency signal transmitting and receivingapparatus.

This application is a division of my applica-- tion Serial No. 123,453filed February 1, 1937, for Automatic tuning system and apparatus.

One of the objects of my invention is to prou vide an automatic tuningsystem for high frequency signal transmitting and receiving apparatus.

Another object of my invention is to provide a circuit arrangement for-controlling the opera- 1' tion of anautomatic tuning system for highfrequency signal transmitting and receiving apparatus by which the powersupply to the apparatus is disconnnected at the start of the automaticoperation of the system and recon- 20 nected after the completion of theautomatic tuning adjustment.

Other and further objects of my invention reside in the circuitarrangement for the automatic control of the power supply and the tuningadjustments of signal transmitting and receiving apparatus as set forthmore fully in the specification hereinafter following by reference tothe accompanying drawings in which:

Figure 1' is a side elevation view of the shaft 30 positioning mechanismof the automatic control system of my invention with the casing thereforbroken away to show the stop rings and the adjustable stop; Fig. 2 is afront elevation of a panel arrangement showing a plurality of shaft 35positioning mechanisms mounted thereon and interconnected with anautomatic setting device enclosed within the broken line and shown indetail in Fig. 8; Fig. 3 is avertical longitudinal sectional view of theshaft positioning mecha- 40 nism; Fig. 4 is a detailed horizontalsectional view therein taken substantially on line 4 -4 in Fig. 3; Fig.5 is a cross sectional view of the shaft positioning mechanism on line5-5 in Fig. 3; Fig. 6 is another cross sectional view thereof 45 on line6--B in Fig. 3, showing in end elevation the stop ring assembly of theshaft positioning mechanism; Fig. '7 is a view similar to Fig. 6 showingthe stop ring assembly in home position with the path clear for movementof the sea lector stop; Fig. 8 is a schematic diagram showing a motordrive, relay and switch arrangement for automatically operating theshaft positioning mechanism in accordance with a prearranged cycle andembodying my invention; and Figs. 9 and 10 are detailed schematicdiagrams of the cam switch of Fig. 8 in different phases of operation.

The principal object of this invention is the automatic tuning of a highfrequency signal transmitter or receiver having a plurality of 5 tuningcontrols, so that it may operate on a number of predeterminedfrequencies. I will describe the application of my inventionspecifically to a, transmitter, although it is apparent that applicationto devices other than trans- 10 mitters can be made. The problem ofshifting the operating frequency of a transmitter is a very importantone, especially on high frequencies, where the frequencies must bechangedfrom time to time during the day in order to obtain satisfactorycommunication. It is also desirable to shift the frequency of thetransmitter rapidly in order to handle trafiic on more than one channelwith a single transmitter. Up to the present time, transmitters havebeen ar- 20 ranged for multi-frequency operation by providing separatelytuned circuits for each frequency, and some form of switching means forselecting the desired set-of tuned circuits. This system has practicallimitations because of the complexity of circuit connections andswitching ap paratus which must be used in a multi-stage transmitteroperating on more than two or three frequencies.

The arrangement of my invention overcomes the practical diflicultiesinherent in previous systems, and, in addition, is compact and flexiblein adjustment. This arrangement consists essentially of a system ofmechanical positioning mechanisms applied to the rotating shafts of theadjustable tuning units of the transmitters, and interconnected in sucha way with suitable actuating means that a group of dialed energyimpulses will act to position each of the tuning shafts to the desiredangular position correspondv ing to the correct adjustment for eachfrequency. The angular position of each tuning shaft may beindependently predetermined for ten or more independent tuningadjustments, and alike number of different frequencies may thus beselected by corresponding groups of dialed impulses.

' Referring to the drawings in more detail, Figs.

1 and 3-7 illustrate a positioning assembly adapted to be associatedwith each rotating element of a radio transmitter as indicated in Fig.60 2. A drive shaft I is directly connected to the shaft of a tuningelement such as a variable condenser, not shown. As illustratedparticularly in Fig. 3, there are-mounted coaxially on this shaft awheel gear 2, a clutch plate I, a

clutch spring 4, a collar 5, a collar retainer ,6, a stop ring cylinder1, a series of stop rings IT, 8a, 8b, 8c, 87', a series of stop ringspacers 9a, 9b, 9c, 9k, and a locking ring Ill. The stop ring cylinder 1is fixed to the clutch plate 3, preferably by screw threads, as shown,and this assembly iskeyed or splined as at I a to the drive shaft I sothat it is free to move axially on the drive shaft, but is not free torotate with respect to the drive shaft. Clutch spring 4 maintainspressure between the clutch plate 3 and the worm wheel gear 2, while thecollar 5 and retainer 6 shown more clearly in Fig. 6, provide a fixedabutment for the clutch spring 4. The worm wheel gear 2 engages a wormgear ll mounted on a drive shaft 49, so that the rotation of the wormgear is transmitted by frictional engagement between the worm wheel gear2 and clutch plate 3 to the shaft I.

A stop carriage I2 having a projecting stop [2a is free to move on theguide I3 under action of lead screw M, in a line parallel to drive shaftI. Lead screw 14 is rotated by selector shaft l6 through the action ofbevel gears l5a and IE1). Stop in is shaped to engage a projecting toothoneach of the stop rings 8a, 8b, 8c, 89' selectively; the selector shaftI 6 being rotated to bring the stop in the plane of the selected stopring. The angular position of thetooth on each stop ring is pre-set byloosening the locking ring I ll, screw-threaded on the cylinder I, androtating the respective stop rings. spacers 9a, 9b, 9c, 970, are keyedinto the stop ring cylinder 1, as by key la, so that manual rotation ofa single stop ring, when the locldng ring I0 is loosened, will notdisturb the positions of adjacent stop rings. Stop ring ll engages the"homing stop I 8, as shown particularly in Fig. 7, at the initial orhome" position of drive shaft I, in which position stop I 2a is free tomove on guide 13 without interference with the teeth or stop rings 8a,8b, 8c, 87', which are never set in the same angular positions and whichtherefore may block the movement of the stop In, as is evident from Fig.6. Knob l9 and graduated or calibrated dial 20 are rigidly affixed todrive shaft i and serve for manual rotation of the drive shaft, and forindication of its angular position by reference to a dial indicator 2|.

The mechanism just described is preferably assembled on a cast base 22,a base plate 25, and a front plate 23, supported by posts 24a, 24d, inspaced relation with respect to base plate 25. Shaft bearings arepreferably of the anti-friction type, incorporating self lubricatingdust seals, and the device may be inclosed by an extruded metal cover asindicated.

A positioning mechanism as just described is provided for each tuningelement of the trans-- mitter as broadly shown in Fig. 2. These tuningelements may consist of variable condensers, variable inductors,rotating switches, etc. and any desired number of positioning mechanismsmay be used, one for each adjustable tuning control. The worm driveshafts 49 of each positioning mechanism are interconnected by suitablelight shafting 49a. as shown, so that the worm drive shafts on all ofthe positioning mechanisms rotate in unison. The selector shafts l6 arelikewise linked together by means of a separate system of shafting in,so that rotation of this shaft system brings the stops i2a into theplanes of corresponding stop rings simultaneously on all of flexibleshafting, or rigid shafting with a system The stop ring of angular gearsand universal couplings, may be used to allow each of the positioningmechanisms to be conveniently disposed with respect to its tuningcontrol. Automatic means for actuating the shaft systems 49a and lid isindicated within the broken line box in Fig.) and fully shownschematically in Figs. 8, 9 and 10.

Referring now particularly to Fig. 8, the system of shafti'ng associatedwith worm drive shaft 49 is mechanically connected to reversible motor26. Also mechanically connected through suitable gearing to the wormdrive shaft system and motor 26 is a cam 21, the lobes of which operatecam switch 28. The system of shafting associated with selector shafts I6is mechanically connected to reversible motor 29. Also mechanicallygeared to the selector shaft system and motor 29 is positioning switch30. An impulse dial switch 3| is shown in operative relation with aminor switch 32 having working contacts 32a, 32b, 327', off-normalcontact 32, operating coil 33, and release coil 34. Fig. 8 also showsmotor control relays 35, 36, 31 and 38; operation sequence relays 38, 40and 4|; and manual master control switch 42; the operations of which arehereinafter defined.

Selector shaft positioning switch 30 comprises two metallic segments 45,4B, separated by an insulating segment 41, mounted on a disk memberrotated by the operation of motor 29. A plurality of contact points 48a,48b, 489', are arranged to make contact with segments 45, 46, 41, andproportions are such that insulating segment 4! can be in contact withonly one contact point 48a, 48b, 487', at any given position of theselector shaft system. The entire selector shaft system is such thatcontact with segments 45, 46, 41, and proportions are such thatinsulating segment 41 can be in contact with only one contact point 48a,48b, 48 at any given position of the selector shaft system. The entireselector shaft system is such that contact between insulating segment4'! and one of the contact points 48a, 48b, 487, corresponds to theposition of selector stop [2a, with reference to one of the stop rings8a, 8b, 87', so that when insulating segment 41 touches contact 480, for

example, stop l2a is in the same plane as stop ring 80.

Two sources of electrical energy may be used for operating the system.These sources are represented as alternator 43, which may be incommercial power circuits, for operating the motors; and rectifier 44,which may be connected to commercial power circuits through atransformer 50, as indicated. It is understood that the rectifier isemployed to obtain direct current for operation of the various relays,as their design may be simplified by the use of direct current. A singlesource of electrical energy, such as a low voltage battery, may be usedfor both the motors and the. relays.

One terminal of operating coil 33 is connected directly to rectifier 44;and the circuit is completed through dial switch 3! and lead 52 back tothe rectifier 44. The release coil 34 is connected through lead SI andswitch contacts 421) or 42c to one side of the rectifier 44; and thecircuit is completed through the upper terminals 39a and 4m of sequencerelays 39 and 4|, respectively, and lead 52 back to the rectifier 44.

Motor control relay 35 is connected through switch 42 contacts 42b or420 to one side of the rectifier 44; and the circuit is completedthrough the intermediate contacts 40b of sequence relay -Motor controlrelay 36 is connected through the lower contacts 391) of sequence relay38 and switch contacts 42b or 420 to one side of the rectifier 44; andthe circuit is completed through the cam switch 28!), lead 53, the uppercontacts 4|a of sequence relay 4|, and lead 52 back to the rectifier 44.Another circuit for relay 36 may be completed through separate contacts42a in man-- ual switch 42, the lower contacts 480 of sequence relay 40,lead 53, and contacts 4|aand lead 52, as above, back to rectifier 44.

I Motor control relays 31 and 38 are connected with one side of therectifier 44 through lead 54, cam switch 28a, lead 53, contacts 4|a ofsequence control relay 4|, and lead 52. A circuit to relay 31 or relay38 is separately completed through segmental contact 45 or 46,respectively, any one of contacts 48a 48a and the corresponding one ofcontacts 32a 329', the contact arm of minor switch '32, lead and switchcontacts 4213 or 420, back to the rectifier 44.

Sequence control relay 39 is connected through lead 5|, and-switchcontacts42b or 420 to one side of the rectifier 44; and the circuit iscompleted through cam switch 28c, auxiliary contacts 350 on motorcontrolrelay 35, lead 53, con

tacts 4|a. of sequence control relay 4|, and lead 52 back to rectifier44. Another circuit for relay 39 may be completed through separatecontacts 42d in manual switch 42; thence to relay contacts 35c and backto the rectifier 44, as above.

Sequence control relay 40 is connected through lead 5| and switchcontacts 421) or 420 to one side of the rectifier 44; and the circuit iscompleted through auxiliary contacts 38b and 31b on motor control relays38 and 31, respectively, lead 54, cam switch 28a and lead 53, sequencerelay.

contacts 4| a, and lead 52 back to the rectifier 44. A self-maintainedshunt circuit for relay 40 is provided through the auxiliary contacts onrelays 38 and 31, the upper contacts 40a on relay 40 itself, and lead53, contacts Ma. and lead 52, as above, back to the rectifier 44.

Sequence control relay'4l is connected through lead 5| and switchcontacts 42b or 420 to one side of the rectifier 44; and the circuit iscompleted through the off-normal contacts 32' of minor switch 32, andlead 52 back to the rectifier 44.

Reversible motor 26 is connected directly with one side of source 43;and the circuit is completed for forward or reverse operation throughseparate contacts 35a and 3517, respectively, on motor control relay 35,and series contacts 36a on motor control relay 36 back to the source 43.Reversible motor 29 is connected directly to one side of the source 43;and the circuit is completed for forward operation through relaycontacts 31a, or for reverse operation through relay contacts 38a, backto the source 43.

The sequence of operation of the system is as follows: Assuming that thestop rings on each of the positioning mechanisms have been fixed inaccordance with manual adjustment for each frequency desired, and thatthe transmitter is in operation on the frequency corresponding to stoprings 8a. The cam 21 will be in operating position with respect to thecam switch 28; that is, the switch actuating member contacts the raisedcam lobe 21a, and the lower switch contacts-28b and 28c are closed, asin Fig. 8. To facilitate description, I will hereinafter refer to thecam switch 28 as having a single pole, double throw, (SPDT) portion28c-b, and a single pole,

single throw, (SPST) portion 28c. In the "operating position of theswitch 28 therefore, the

SPDT portion has the lower contacts 281) closed, and the SPST portion280 is closed.

To effect a different frequency adjustment, the operator dials, saynumber 5 corresponding to another frequency-of operation, whichproduces, by means of the impulse device 3|, five impulses. Each impulsemoves the contact arm on minor switch 32 one step, through the action ofoperating coil 33, so that the contact arm reaches the fifth contact32c, as shown by dotted line in. Fig. 8. This action also closes theoffnormal contact 32 of the minor switch 32. Now

assuming manual switch 42 in its lower position operating the upper setsof contacts 42a and 421), then sequence relay 4| is energized throughconductors 5| and 52, andthe upper contacts 4|a thereof complete acircuit to conductor 53 to operate worm drive shaft motor control relay36 through the lower contacts 28b of the SPDT portion of switch 28, andthe lower contacts 39b of relay 39 which are normally closed. Operationof relay contacts 36a applies power to motor.26 through the normallyclosed lower contacts 351) of motor control relay 35, and the motoroperates to rotate the worm drive shaft system 49a and cam 21 in areverse direction so as to bring all of the stop rings |1 against home"stops l8. During this interval the cam-switch actuating member rides onthe running portion 21b of the cam 21; and the SPDT portion of switch 28will have the lower contacts 28b closed but the SPST portion 280 willhave been opened. This condition of the cam and cam switch isillustrated-in Fig. 9.

It is to be noted, that drive shafts of each of the positioningmechanisms will rotate through various angles before reaching homeposition, depending upon their previous set positions, but in no casewill any of the drive shafts be required to rotate through more than,say 180. The clutch arrangement on each of the drive shaft assembliesprevents interference with the rotation of any of the positioningmechanisms by reason of limitations in any one of them; so that, forexample, if the positioning mechanism which has rotated through thesmallest angle to reach home position has done so, the clutch in thatpositioning mechanism permits its worm and wheel gearing to continue torotate so that the others of the mechanisms may reach their homepositions.

Cam 21 is shaped so that it operates the cam switch 28 after the wormshaft system has rotated through an angular displacement correspondingto a rotation of any drive shaft of approximately 200, which rotation issufllcient to return all of the positioning mechanisms to the homeposition. This portion of the cam 21 consists of a depression 210, andupon being engaged with the cam switch actuating member causes the uppercontacts 28a. of the SPDT portion of the cam switch to close, the SPSTportion 280 remaining open. This condition of the cam and cam switch isillustrated in Fig. 10. Operation of the SPDT portionv of the cam switch28, thus acts to deenergize relay 36, therefore stopping motor 26, andalso to complete circuits by way of contacts 28a and conductor 54through relays 31 and 38, positioning switch 30, and minor switch 32,and through relay 40, to conductor 5|. v

If the minor switch 32 is set on the fifth contact 32e, as supposed,current can only flow from conductor 5| through the fifth contact point488 on selector switch 30. If a circuit is completed through contact43c, segment 45, and motor control relay 31, the selector shaft motor 29is energized through contact 3111 and caused to rotate in such adirection that insulating segment 41 moves toward contact 498. Wheninsulating segment 41 touches contact 48c, the circuit through relay 31is broken, and the motor 29 and selector shafts i6 cease rotating withthe stops l2a positioned opposite stop rings So. If, due to mechanicalinertia, insulating segment 41 is carried past contact point 496, orshould the segment 41 have been originally beyond the contact 4861, sayat contact 437', then a circuit is completed including contact 48c,segment 45, and motor control relay 99, causing motor 29 to be energizedthrough contacts 38a and to rotate in the opposite direction untilinsulating segment 4'! meets contact 49c.

The auxiliary contacts 31b and 381) on relays 31 and 33 are connected inseries with the operating coil 01' sequence relay 40, which relay isdesigned 'to operate only after it has been energized for apredetermined time interval, which may be a fraction of a second. Thus,after the insulating segment 41 of selector switch 30 has interruptedthe connection to the fifth contact 486 for this predetermined interval,during which neither relay 31 or 39. will be operated and the mechanicalsystem associated with the selector shafting will have come to rest,sequence relay 40 will operate. The upper group of contacts 40a of relay40 upon being closed provide a separate circuit for energizing the coilof relay 40 from conductors 5i and 53, and the relay 40 thus will remainoperative after conductor 54 becomes disconnected at contacts 280 fromconductor 53 and the power supply by operation of the SPDT portion ofcam switch 23.

The lower two groups of contacts band 40c 01 sequence relay 40 completecircuits from conductor 53 to energize relays 35 and 36 separately,which apply power to motor 26 for running it in a forward" direction, asdetermined by the upper contacts 35a of relay 35, for a periodcorresponding to approximately 200 rotation of any drive shaft I, asaforesaid during which interval, cam 21 is rotating in a spendingamount. During this forward movement of the cam, the cam switchactuating member again rides on the running portion 21b of the cam 21,and eventually meets the raised cam lobe 21a in the operating portion01' the cam which actuates cam switch 28 so that the SPST portion 230 isclosed, the SPDT portion being conditioned, with the lower contacts 23bclosed, for future operations. Operation of the SPST portion 23c or thecam switch, in series with the closed auxiliary contacts 350 of relay35, which remain closedbecause relay 40 remains energized, completes acircuit which operates relay 39 for closing contacts 390 whichmomentarily operate to energize release coil 34 of the minor switch 32,and remove power from the entire system. Relays 4|, 43, 39 and 35, whenonce energized at their respective points in the cycle, remain operativeuntil action of the minor switch release coil 34 has restored the minorswitch and opened the off-normal contact 32, thus removing power fromthe entire sequence relay circuit. When this has taken place, no furtheraction or either motor can occur until the minor switch is againactuated.

The sequence relay 4| has auxiliary contacts at 55 which remove powerfrom the transmitter "iorward direction in a corre- 2,1so,sea

itself at the beginning of the automatic tuning cycle and re-apply powerto the transmitter at the completion of the tuning cycle.

Manual switch 42 when in center position allows the minor switch to beset up, but prevents further operation. When in the lower position,operating the upper set of contacts, 42a, 42b, normal operation isobtained, as hereinbefore described. When in the upper position,operating the lower set of contacts, 42c, 42d, the cycle takes place upto the energization of relay 35 through the middle contacts 401) ofrelay 4!), which closes the auxiliary contacts 35con relay 35. A circuitis thereby completed through relay 39 by way of the lowermost contacts42d of switch 42 and all power is removed from the system. The stoprings 8a, 8b, 87', are thus left in home" position. but the stops are inthe position corresponding to the number dialed. This part-cycleoperation is employed when adjusting the stop rings after tuning thetransmitter, the stop rings corresponding to the position of the stopsbeing manually rotated until they abut the stops, with the instrumentshafts in adjusted positions for one desired frequency. This operationmay then be successively repeated for adjustment of the other stop ringsfor diflerent frequencies.

The full cycle of operation of the automatic positioning device may bedescribed less specifically as follows: An impulse transmitter of thekind commonly used for dial telephone circuits is operated to send aseries of impulses to a system of control relays. The control relaysinfluence the operation of two motors so that: first, the tuning controlshafts of the transmitter are rotated in a "reverse direction andreturned to home" position; second, the stops on all of the positioningmechanisms are moved into the planes of the stop rings, adjusted for thedesired frequency; third the tuning shafts are rotated in a forwarddirection until all of the corresponding stop rings are rotated intocontact with the stops, bringing each tuning element into the desiredangular position. It is possible to construct a system as describedwhich will complete the cycle of operations between the tuningadjustment for one frequency and that of another frequency in fiveseconds or less.

' It is to be understood that many modifications can be made in theapparatus without departing from the plan of my invention. For example,the stops engaging the stop rings can be moved by means 01' a rack andpinion instead of by means of a lead screw as described heretofore; orthe stops can be moved into position by means 01' a solenoid, ratchetand pawl actuated by the dial impulses. A further possible modificationof my system is to place the slip clutch on the worm drive shaft ratherthan on the instrument shalt. Another modification is to utilize amulti-point manual switch in place of a minor switch. Another possiblemodification is the use of separate magnetic latches actuatedselectively to engage the stop rings in place of a single mechanicalstop moved from the plane of one stop ring to that of another. A furthermodification of my invention involves the use of a single motor insteadof two with a selective transmission, so that the single motor actuatesthe worm drive shaft system and the selector shaft system alternately.However, as the power requirements of the motors are small, it is moreconvenient to employ two motors as described above than to use a singlemotor with selective transmission. The specific embodiment I havedisclosed has practical merit, but modificationing the shaft in selectedposition, electrical motor means for setting said movable stop invalignment with said stop means, motor means for rotating said shaft andsaid stop means with respect to the movable stop, and automaticelectrical control means connected with said source of power and withboth said motor means and operative in a predetermined sequence forremoving power from the apparatus, actuating said motor means toestablish the shaft in desired position while power is removed from theapparatus, and applying power again to the apparatus. 2. In combination,shaft-controlled electrical apparatus connected with a source of power,a plurality of stop means adiustably mounted on the shaft of saidapparatus, a movable stop adapted for coaction with a selected one ofsaid stop means, and means for separately rotating said shaft and movingsaid stop, and an automatic electrical control system includingrelayswitch means for controlling the application of power from said sourceto said apparatus, and a cam and switch device for controlling saidshaft and said stop in a predetermined sequence of operation precededand succeeded by operation or San relay switch means, for establishingsaid shaft in desired position. v r

3. In combination, shaft-controlled electrical apparatus connected witha source of power; a plurality-of stop means adjustably mounted on theshaft of said apparatus, a movable stop adapted for coaction with aselected one of said.

stop means, and means for separately rotating said shaft and moving saidstop; and an automatic electrical control system including relay switchmeans for controlling the application of power from said source to saidapparatus, a cam and switch device for controlling the operation of saidshaft and said stop, and a manually operable switch device connected insaid control system; said system being operative under control of saidmanually operable switch device in a sequence of operations to removepower from the apparatus, establish the shaft in a home" position andmove said stop to a predetermined selected position for adjustment ofthe corresponding stop means, said system subsequently being operativeunder control of said manually operable switch device in a full cycle ofoperation for establishing the shaft in a position determined by aselected one of the adjusted stop means.

4. In combination, in a shaft positioning system, shaft-controlledelectrical apparatus connected with a source of power; a plurality ofstop means for the shaft of said apparatus, a movable coacting stop, andmeans for separately rotating said shaft and moving said stop; and anautomatic electrical control system including an impulse-actuated minorswitch having ofinormal contacts for initiating operation of saidcontrol system, a relay-device controlled by said oif-normal contactsand having switch contacts connected in circuit with said source ofpower and said apparatus and operable by said relay device forcontrolling the application of power to said apparatus, and additionalswitch contacts operable by said relay device and connected in saidcontrol system as an element thereof for actuating said means forseparately rotating said shaft and moving said stop in a predeterminedsequence of operations to establish said shaft in a desired position.

. 40 ARTHUR ACOUJNS.

